When replacing an tire with a automobile tire changer, at first it is required to separate a bead of the tire from a rim using an assistant arm for the tire changer, thereby to disassemble and assemble the tire. During the disassembly and the assembly, such a requisite and complex step as “tire pressing” is also required. In a sense, the assistant arm plays a very important role in the properties of the automobile tire changer.
Currently, there are two kinds of assistant arms. One is of a one-for-one type, i.e., one longitudinal actuator is used to actuate one tire pressing mechanism provided with a bead separator. This tire pressing mechanism is further provided with a turn-over function so as to facilitate the separation of the beads at two ends of the tire. This assistant arm is less automatic and has a complex structure, so it will take more effort to carry out the turn-over operation. The other is of a two-for-two type, i.e., two longitudinal actuators are used to actuate two identical tire pressing mechanisms each provided with a bead separator, respectively. The two tire pressing mechanisms can move up and down independently of each other and meanwhile the bead separators can synchronous move laterally, so as to facilitate the separation of the beads at the two ends of the tire without the turn-over function. The synchronous lateral movement of the bead separators is achieved by a fixed push-pull flexible shaft. This assistant arm is more automatic, but it is very expensive and its control system is very complex.
The tire pressing mechanism of the existing assistant arm moves along a longitudinal direction of a guide rail member. Currently, there are two kinds of guide rail members. One is made of a fine, square steel profile. Because there are very strict requirements on the precision, this steel profile is very expensive and used rarely. The other is formed by welding a guide rail with an anti-buckling beam. This guide rail member is cheap and of a simple structure, so it has been widely used. However, due to a long welding seam along the guide rail, there exists great post-welding deformation for the guide rail member, and it is difficult to correct the deformation after the welding. In addition, even when the deformation is corrected, the precision loss may occur too. As a result, when a mobile member moves along the guide rail member, a so-called “crawling phenomenon” will occur, and the tire disassembly and assembly procedures will be adversely affected, resulting in a hidden peril of the accident.